Crigler-Najjar Syndrome

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Crigler-Najjar syndrome comprises two distinct syndromes of congenital unconjugated hyperbilirubinaemia, due to an inborn error of bilirubin metabolism. There is deficient activity of the enzyme uridine diphosphate glucuronosyltransferase (UGT), resulting in an impairment of the ability to conjugate and excrete bilirubin. There are mutations in the structure of the gene, whose locus is on the long arm of chromosome 2.[1, 2] This leads to either virtually absent enzyme activity (type I) or impaired activity (type II). It is a rare disease with only hundreds of reported cases worldwide.

UGT1A1 is the only enzyme catalysing the generation of water-soluble bilirubin glucuronides in hepatocytes. Therefore, mutations in this gene lead to deficiencies in bilirubin conjugation and excretion.[3]

Crigler-Najjar syndrome involves two very rare (less than 1/106 live births) autosomal recessive disorders (types I and II), which differ in the degree of UGT1A1 deficit and consequently in the clinical presentation.[5]

Type II appears to be more common than type I but it is still an unusual sporadic disease.

Gilbert's syndrome is much more common.

Isolation of parents and medical/allied professionals working in the field has been a bar to progress in treatment and research but is improving due to the institution of international conferences for all interested parties.

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